How To Preserve Values In ASPX Page

I am trying to figure out how to preserve the values of the controls on this page (just the user-submitted commission value and the sales region (eastern is 10% and western is 20%)).

The code is as follows:

<form id='frmShowCommSingleDocKeepState' action='afShowCommSingleDocKeepState.aspx' method='get' >
<div>
<%
Dim strSale As String
Dim dblSale As Double
Dim strRegion As String
Dim dblComm As Double
Dim E As Double = 0.1
Dim W As Double = 0.2........